Occurring at the start of France's main vacation period, the wreck stuns the country

PARIS—French state railway operator SNCF said Saturday that an investigation into the train accident that caused at least six deaths near the French capital was focusing on a possibly faulty railroad switch.

The accident occurred Friday evening as the train with 385 passengers went off rail while traveling at a high speed through the Brétigny-sur-Orge station, about 15 miles south of Paris.